Configurable wasm builds

[CyberHoward]

Updated version of #130

The need for featured contract compilation has been thoroughly discussed in issue #80. This PR upstreams the ability to optimize smart-contracts with different features, without hurting reproducibility.

Example

As an example let's say you have some functionality that should only be enabled on some specific chain. Currently it's extremely hard to do this without creating different contracts.

Our solution uses cargo's support for custom metadata fields to allow you to specify features that you want your contract to be built with.

I.e. if I want different logic when deploying to the cw-sdk then I add a feature in the contract's Cargo.toml like so:

[features]
cw-sdk = []

To trigger the optimizer into building the contract with this feature add the following to the same Cargo.toml:

[package.metadata.optimizer]
default-build = true
builds = [
  { name = "cw-sdk", features = [
    "cw-sdk",
  ], default-features = false }
]

After running the optimizer image as usual you will be left with:

• my_contract.wasm
• my_contract-cw-sdk.wasm

When using the ARM image:

• my_contract-aarch64.wasm
• my_contract-cw-sdk-aarch64.wasm

Extra features

• @apollo-sturdy requested the ability to disable WASM compilation with default features. This is solved by the default-build boolean. (defaults to true)
• A suggestion was made in the previous PR to add WASM optimization configuration to this metadata. This currently can't be done as the optimization call is executed from the optimize.sh script which is not under control of the Rust code. This could be changed in a future PR.
• A build can disable default features with the default-features = false attribute.

Discussion

Some questions were raised about the additional caching layer that prevents re-build if the build settings are identical. I left this caching layer in place because we (Abstract) make extensive use of it. See here. However as mentioned re-building a previously built package shouldn't take much time. Edit: We decided to remove this layer.

[apollo-sturdy]

@webmaster128 Any chance you have time to review and merge this? Would be very helpful for us.

[CyberHoward]

Applied feedback, thanks!

@apollo-sturdy for the default-build, do you want the ability to build without default features or does the current solution work for you?

[webmaster128]

Not directly related but FYI I think we should get rid of the aarch64 suffixes at some point. I don't think they have value anymore. https://github.com/CosmWasm/optimizer/issues/151

[webmaster128]

Cool!

Last question here: are we happy with the naming "default-features" and "default-build" to close to each other? Isn't this likely to cause confusion amongst contract devs who don't have a very clear understanding of how those things relate to each other? Should we rename one, e.g. "default-build" -> "standard-build"?

[webmaster128]

I'll merge this now and then change the terms to

• standard-build
• default-features

in a separate PR. Feel free to disagree and let me know.

Thanks a lot for this contributions!

[webmaster128]

Follow-up work is here: https://github.com/CosmWasm/optimizer/pull/156

[ethanfrey]

Great job @CyberHoward